The universal mobile telecommunications system (UMTS) is a third-generation mobile communications system evolving from the global system for mobile communications system (GSM), which is the European standard. The UMTS is aimed at providing enhanced mobile communications services based on the GSM core network and wideband code-division multiple-access (W-CDMA) technologies.
FIG. 1 gives an overview of the UMTS network, including the UE, the UTRAN and the core network (CN). The UTRAN is composed of several radio network controllers (RNCs) and Node-Bs, which communicate via the Iub interface.
Each RNC controls several Node-Bs. Each RNC is connected via the IU interface to the core network (CN), specifically to the MSC (Mobile-services Switching Center) and the SGSN (Serving GPRS Support Node) of the CN. RNCs can be connected to other RNCs via the Iur interface. The RNC handles the assignment and management of radio resources and operates as an access point with respect to the core network.
The Node-Bs receive information sent by the physical layer of the terminal through an uplink transmission and transmit data to the terminal through a downlink transmission. The Node-Bs operate as access points of the UTRAN for the terminal.
The SGSN is connected via the Gf interface to the EIR (Equipment Identity Register), via the GS interface to the MSC, via the GN interface to the GGSN (Gateway GPRS Support Node) and via the GR interface to the HSS (Home Subscriber Server). The EIR maintains lists of mobiles that are allowed to be used on the network.
The MSC controls the connection for circuit switch (CS) services. The MSC is connected to the MGW (Media Gateway) via the NB interface, to the EIR via the F interface, and to the HSS via the D interface. The MGW is connected to the HSS via the C interface and to the PSTN (Public Switched Telephone Network). The MGW facilitates the adapting of the codecs between the PSTN and the connected RAN.
The GGSN is connected to the HSS via the GC interface and to the Internet via the GI interface. The GGSN is responsible for routing, charging and separation of data flows into different radio access bearers (RABs). The HSS handles the subscription data of the users.
The UTRAN establishes and maintains a radio access bearer (an RAB) for communication between the terminal and the core network. The core network requests end-to-end quality of service (QoS) requirements from the RAB and the RAB supports the QoS requirements set by the core network. Accordingly, the UTRAN can satisfy the end-to-end QoS requirements by constructing and maintaining the RAB.
The services provided to a specific terminal are roughly divided into circuit switched (CS) services and packet switched (PS) services. For example, a general voice conversation service is a circuit switched service, while a Web browsing service via an Internet connection is classified as a packet switched (PS) service.
For supporting circuit switched services, the RNCs are connected to the mobile switching center (MSC) of the core network and the MSC is connected to the gateway mobile switching center (GMSC) that manages the connection with other networks. For supporting packet switched services, the RNCs are connected to the serving general packet radio service (GPRS) support node (SGSN) and the gateway GPRS support node (GGSN) of the core network. The SGSN supports the packet communications with the RNCs and the GGSN manages the connection with other packet switched networks, such as the Internet.
FIG. 2 illustrates an architecture of a radio interface protocol between the terminal and the UTRAN according to the 3GPP radio access network standards. As shown in FIG. 2, the radio interface protocol has vertical layers comprising a physical layer, a data link layer, and a network layer, and has horizontal planes comprising a user plane (U-plane) for transmitting user data and a control plane (C-plane) for transmitting control information.
The user plane handles traffic information with the user, such as voice or Internet protocol (IP) packets. The control plane handles control information for an interface with a network, maintenance and management of a call, and the like. The protocol layers in FIG. 2 can be divided into a first layer (L1), a second layer (L2), and a third layer (L3) based on the three lower layers of an open system interconnection (OSI) standard model. The first layer (L1), or the physical layer, provides an information transfer service to an upper layer by using various radio transmission techniques. The physical layer is connected to an upper layer, called a medium access control (MAC) layer, via a transport channel.
The MAC layer and the physical layer exchange data via the transport channel. The second layer (L2) includes a MAC layer, a radio link control (RLC) layer, a broadcast/multicast control (BMC) layer and a packet data convergence protocol (PDCP) layer.
The MAC layer handles mapping between logical channels and transport channels and provides allocation of the MAC parameters for allocation and re-allocation of radio resources. The MAC layer is connected to an upper layer, called the radio link control (RLC) layer, via a logical channel.
Various logical channels are provided according to the type of information transmitted. In general, a control channel is used to transmit information of the control plane and a traffic channel is used to transmit information of the user plane.
A logical channel may be a common channel or a dedicated channel depending on whether the logical channel is shared. Logical channels include a dedicated traffic channel (DTCH), a dedicated control channel (DCCH), a common traffic channel (CTCH), a common control channel (CCCH), a broadcast control channel (BCCH) and a paging control channel (PCCH) or a Shared Channel Control Channel.
The BCCH provides information including information utilized by a terminal to access a system. The PCCH is used by the UTRAN to access a terminal.
The possible mapping between the logical channels and the transport channels from a UE perspective is given in FIG. 3. The possible mapping between the logical channels and the transport channels from a UTRAN perspective is given in FIG. 4.
The MAC-d sub-layer manages a dedicated channel (DCH), which is a dedicated transport channel for a specific terminal. The MAC-d sub-layer is located in a serving RNC (SRNC) that manages a corresponding terminal. One MAC-d sub-layer also exists in each terminal.
The RLC layer, depending of the RLC mode of operation, supports reliable data transmissions and performs segmentation and concatenation on a plurality of RLC service data units (SDUs) delivered from an upper layer. When the RLC layer receives the RLC SDUs from the upper layer, the RLC layer adjusts the size of each RLC SDU in an appropriate manner based upon processing capacity and then creates data units by adding header information thereto. The data units, called protocol data units (PDUs), are transferred to the MAC layer via a logical channel. The RLC layer includes a RLC buffer for storing the RLC SDUs and/or the RLC PDUs.
The BMC layer schedules a cell broadcast (CB) message transferred from the core network and broadcasts the CB message to terminals positioned in a specific cell or cells.
The PDCP layer is located above the RLC layer. The PDCP layer is used to transmit network protocol data, such as the IPv4 or IPv6, effectively on a radio interface with a relatively small bandwidth. For this purpose, the PDCP layer reduces unnecessary control information used in a wired network, by using a function called header compression.
The radio resource control (RRC) layer located at the lowest portion of the third layer (L3) is only defined in the control plane. The RRC layer controls the transport channels and the physical channels in relation to setup, reconfiguration, and the release or cancellation of the radio bearers (RBs). Additionally the RRC handles user mobility within the RAN and additional services, such as location services.
The RB signifies a service provided by the second layer (L2) for data transmission between the terminal and the UTRAN. In general, the set up of the RB refers to the process of stipulating the characteristics of a protocol layer and a channel required for providing a specific data service, and setting the respective detailed parameters and operation methods.
The different possibilities that exist for the mapping between the radio bearers and the transport channels for a given UE are not all possible all the time. The UE and UTRAN deduce the possible mapping depending on the UE state and the procedure that the UE and UTRAN are executing. The different states and modes are explained in more detail below, as far as they concern the present invention.
The different transport channels are mapped onto different physical channels. For example, the RACH transport channel is mapped on a given PRACH, the DCH can be mapped on the DPCH, the FACH and the PCH can be mapped on the S-CCPCH, and the DSCH is mapped on the PDSCH. The configuration of the physical channels is given by RRC signaling exchanged between the RNC and the UE.
In UMTS, as described above, system information is usually broadcasted in system information blocks (SIBs) on a specific channel, and system information is separately sent in different SIBs in order to optimize the reading of the system information. When the different SIBs are transmitted, the transmitted SIBs are indicated in a master information block (MIB) or scheduling blocks. The MIB indicates a position of the scheduling blocks and value tags of the SIBs, and the scheduling blocks indicate scheduling information for the SIBs. The transmission of the MIB, SIB, and scheduling block is scheduled according to the timing of the PCCPCH. The MIB is always sent with a fixed offset related to the PCCPCH and with a fixed repetition period. Therefore, the UE is able to receive information via various channels when such information is needed to be received by the UE according to the fixed repetition period.
The system information which contains certain information, such as configuration of the cells and/or a GSM public land mobile network (PLMN) related information etc., is transported from the network to the UE. Some information is only valid in the cell where the SIB is transmitted, and some other information is valid in the entire network (i.e. PLMN). Therefore, depending upon the types of information, SIBs with information that is valid in the cell must be re-read each time the UE moves to another cell and SIBs with information that is valid in the entire network do not need to be re-read each time the UE moves to a different cell.
Generally, the SIBs can be linked to a timer if the system information changes frequently. These types of SIBs include a timer value such that once the UE has read the SIB, it knows the SIB needs to be re-read after the time indicated by the timer. These types of SIBs are only re-read by the UE when the timer expires. If the timer value is set to infinite, it means that the UE will never re-read those SIBs again after the UE has acquired those SIBs once.
Therefore, in the conventional art, if the timer is set to a finite value, the UE will not re-read SIBs before the timer has expired. This causes an unnecessary time delay for updating the system information. Also, if the timer is set to an infinite value, it is not possible to update the system information stored in the UE unless the UE moves to the new cell or PLMN.
For example, the UE needs to receive system information on the uplink interference in order to access the random access channel (RACH), and the UE uses persistence values during the RACH access. In these procedures, the system information is transmitted in the SIB 7 that is linked to a timer. Usually, this system information is subject to frequent changes, as such, it is necessary that the UE should read up-to-date system information frequently.